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Class 9: WateringOriginal PPT by Gary L. Reum

Adapted by Gia ParsonsPresented by Bruce Williams

The information contained in Growing Groceries presentations is based on WSU home gardening publications and other science and research-based materials. Resource lists are provided on the King County Growing Groceries website and at the end of some presentations.

To enliven the learning experience, speakers may use examples from their own garden experience and draw from their personal gardening successes and failures.

Resources

Why Is Watering Important?

In the PNW, most garden crops need supplemental water in the summer.

The need for irrigation depends on:• The soil’s water holding capacity• Weather• Your garden site• Type of plants grown • Plant growth stage

Why to Water Wisely

Good water management will increase crop yields, improve crop quality, conserve water, save energy, and decrease fertilizer requirements.

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Soil Texture

How far watermoves in the soil depends partly onsoil texture:• Clay soils• Sandy soils• Loamy soils

Clay Soils

• Clay soils drain very slowly and are prone to being over-watered (resulting in drowning and rotting of plants).

• The have a large water holding capacity.

Sandy Soils

• Have limited water holding capacity• Sandy soils are quick to dry out due to their porous nature.• Over watering will result in leaching away important nutrients to below the root zone.

Loamy Soil

A proper mixture of sand, silt, and clay coupled with compost provides

for an idea soil texture for veggies.

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Soil Moisture FactorOn average, plants consume from 0.1 to 0.3 inch

of rainfall or irrigation per daySandy soils: Hold between 0.5-1 in. of water per

foot soilLoams: Hold between 0.8-2 inch per foot soilClays: Hold between 1.3-2.4 inch per foot of soil

Your Garden Site• Full sun• Partial sun• Mostly shade• Trees nearby• On a slope• Uneven ground• Raised beds• Containers

Types of Plants Being Grown

• Sweet corn and lettuce are shallow-rooted and don't do well without a lot of water.

• Many tomatoes actually do better if you cut off irrigation in mid- to late summer.

Watering Needs for Plant Growth Stages

• Germinating seeds and seedlings need uniform moisture, so water daily to keep them moist.

• Developing plants need to be watered deeply but less frequently, to encourage deep root growth.

• Water at least 6 inches deep and then let the surface inch or two completely dry out before watering again.

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Watering Your Garden• Moisten the entire root zone of the plant — the area in which

the plant extends its roots down and out.• Best in the morning, allowing plants to handle the evaporative

effects of sun, wind, and heat throughout the day.• If watering in the evening, make it early to minimize damage

from common fungal diseases such as verticillium wilt. • Slugs are attracted to a wet gardening area with late

watering, early shadow casts, and cooling temperatures.• Consistent watering is critical. Anytime a plant exhibits

drought stress symptoms, don’t wait, it’s time to water.

Early Care of Plants• If it’s hot & sunny when you

plant, your young plants will need extra care – and water

• Water transplants daily at first• Water newly seeded or newly

germinated seedlings 2X/day• Recommend hand watering

with a minimum of 3 passes to ensure a deep watering is achieved.

Depth of Watering

• Shallow watering encourages roots to stick close to the soil surface, thus making plants more vulnerable to drought and weaker.

• Deep watering reaches the depth of the root zone. Deeper, less frequent watering encourages plants to develop deeper roots and a more robust stable plant.

Know Your Plants

• Tomatoes: when mature drink heavily and are deep rooted

• Strawberries: shallow rooted but require more water because they can’t develop deeper roots

• Corn: needs more water during time of tasseling

• Weeds: can consume up to 25% of the water from your soil

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Indicator Plants• Plants having larger leaves will show signs of

wilting when running low on water.• Remember that plants may wilt during the heat

of the day but will make a quick recovery once given some shade.

• General rule: The primary target is the soil at the base of the plant and root zone, not leaves.

• Add a rain gauge to your toolkit of fact-finding data for your microclimate.

Types of Watering Applications

• Rain• Surface irrigation

using furrows or dams

• Overhead watering• Localized watering• Drip irrigation

Overhead Watering

• Sprinklers• Watering cans —

minimum of 3 passes• Most wasteful, up to

70% loss• Evaporative loss,

overspray, unevenness, runoff

• Wets foliage

Furrows and Dams

• Uses a lot of water

• Used in larger scale crop production

• Low tech

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Localized Irrigation• Bottle irrigation

delivers water to the root zone

• Can be a way to recycle bottles

• Inexpensive• Foliage stays dry

Localized Irrigation• Delivers water to

the root zone • Can be a way to

recycle pots• Inexpensive• Foliage stays dry

Localized Irrigation

• Delivers water to the root zone

• Can be adjusted• Relatively

inexpensive• Easy set up• Couple with a timer

Drip Emitters

• Great for specimen plants

• Great for pots and small raised beds

• Works for short rows• Foliage stays dry

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Rain Barrels

Usually slow gravity-fed drip emitters

Localized Irrigation

• Oyas are made of unglazed terra cotta

• An ancient way of watering

• Expensive• May crack in

freezing weather

Ollas

• Roots tend to grow around the olla

• You would need one every 2-4 feet

• Caps prevent evaporation and keep out debris and bugs

Localized Irrigation

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Drip Irrigation• Delivers water

slowly and directly to the root zone

• 90-95% efficient• Covers a wide area• Couple with a timer• Provides consistent

watering

Drip Irrigation• Research the type of drip irrigation• Some spray upwards• You will need adequate water pressure• UV light does break down the irrigation lines

Create and Plan Your Irrigation System• Understand your garden’s requirements• Plan how to run your main water supply to your garden• Divide into zones• Start small and build as you go• Plan transport system (main supply line, hose runs,

splitters, risers, laterals) • Determine diffuser type(s): soaker hoses, emitters, drip

tape and other various drip tubes (line-source, point-source or both)

• Be aware of cost for assembly, replacements, and repairs

Drip Irrigation Systems

Low Tech, Lower Cost

• Soaker hoses• DIY emitter systems• Ollas (expensive)• Simple timer• Manual: use while

you are at the garden

Higher Cost, Set and Forget

• Require more planning

• May need pressure regulator

• Digital timer• Filter• Manifold• Automatic

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Figure 1. Example of drip system components all together. (Numbers match discussion items in text.) 1—Water Source (Control valve is the hose bib); 2—Backflow Prevention Device; 3—Pressure Regulator;

4—Screen Filter; 5—Vacuum Relief Valve; 6, 7—Drip Tubing.

Drip System DesignLine-Source System• Drip emitters spaced at regular intervals along the line• Water comes from one continuous source instead of a

series of drippers• Tubing with pre-installed emitters, drip tape, T-tape

and soaker hoses can all be considered line-sourcePoint-Source System• Individual emitters placed in discrete locations• At the base of the plant = upper root zone area of

plant

Line Source System

• Minimal evaporative loss (non-spray)

• Use markers and run soakers under soil surface 1-3”

• Good for densely spaced crops

• Keep as level as possible• Space closer together in

sandy soils, further apart on clay

Point Source System

• Most efficient systems, up to 98% • Reduces weed growth• Tailor system to garden’s specific needs• Able to water various heights (containers, pots)

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Divide Irrigation into Zones• Break up vegetable garden into different watering zones• Base zones on garden size or varying water demand

rates and/or growing times of different vegetables• Enables more control over where you want the water

and how much water you want applied• Provides ability to swap/change out emitters/diffuser

types for mid-season planting of different vegetables or crop rotation

Timers are Essential• Mandate the use of timers• Saves money (no wasted water)

and time • Without timers, drip irrigation

systems can be easily mismanaged with costly consequences

• Check soil moisture content and set irrigation schedule

• Determine application rates using calculator at

Water According to Your Needs• Hand-watering brings good results during vegetable

germination, sprouting and with initial transplanting• Collect & store water, use for hand watering• Watering early in the day works best• Adjust your watering cycle with the seasons• Consistent watering is critical• Make routine “walk thru” to notice irregularities in soil

and plants• Add a rain gauge & logbook to your toolkit. Take notes

of fact-finding data.

Let’s Debunk a Watering Myth

Reality vs Rumor

Linda Chalker-Scott, Ph.D., Puyallup Research & Extension Center - WSU

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Myth: “Watering plants on a hot sunny day will scorch their leaves”

• We are told that during the hottest months, water drops that accumulate on the leaf surfaces act as tiny magnifying glasses, focusing the sun’s energy into intense beams that burn leaves”

• Additionally, we are told that since water efficiently conducts heat, wet leaf surfaces are more likely to burn than dry ones.

Reality • WSU.edu and other websites dispel this myth, while other

domains on the internet keep this misinformation alive.

• If your plant(s) are showing signs of water stress in the middle of the day, by all means you should water them.

• DO NOT POSTPONE: Postponing watering until the evening or next morning could damage your plant and open them up to opportunistic diseases; watering in the evening can encourage fungal pathogens.

Bottom Line • Wet foliage is not susceptible to sunburn• Anytime plants exhibit drought stress symptoms

it is time to water them• Do not overuse fertilizers & pesticides, especially

those containing sodium or chloride salts• If using recycled water, consider using a filtering

system before applying it to plants

Summary• Observe — be part of the growing experiment• Become a steward of the garden and environment by

conserving water and using it wisely.• Start small and learn from your mistakes — expand

with your increased knowledge & experience — Look, Review, Learn, then Adjust.

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Sources & Image Creditshttp://treefruit.wsu.edu/web-article/soils-and-nutrition/https://puyallup.wsu.edu/soils/soils/http://pubs.cahnrs.wsu.edu/publications/pubs/em063e/?p-page=4http://pubs.cahnrs.wsu.edu/publications/pubs/eb1090/https://pubs.extension.wsu.edu/drip-irrigation-for-the-yard-and-garden

https://extension.oregonstate.edu/news/some-vegetables-require-less-water-othersImage credits on slides:http://www.thepermaculturepodcast.com/2011/pdc-soil-structure/https://www.gardenersworld.com/plants/find-out-your-soil-type/http://www.chanshare.com/wwisoiltips/https://www.express.co.uk/comment/columnists/alan-titchmarsh/922521/gardening-tips-alan-

titchmarsh-soil-quality-clay-sand-loamyhttp://www.farmmanagement.pro/5-methods-of-manipulating-soil-moisture-levels/https://bonnieplants.com/gardening/hot-summer-watering/https://jasongoroncy.com/2012/05/29/afraid-of-roots-and-depths/

Image Credits https://www.duboisag.com/ca_en/250-heavy-duty-drip-irrigation-kit-bioplus.html

https://people-equation.com/toward-a-growth-mindset/

https://www.usgs.gov/media/images/irrigation-methods-furrow-or-flood-irrigation

https://chaletnursery.com/blogs/chalet-blog/potting-techniques-200-level-course

https://en.wikipedia.org/wiki/Drip_irrigation

https://bonnieplants.com/gardening/for-a-plentiful-harvest-keep-pots-watered/

https://www.hunterindustries.com/irrigation-product/micro-irrigation/point-source-drip-emitters

https://thegardendiaries.blog/2012/01/30/rain-barrel-eye-candy/

https://shop.growoya.com/products/large-oya?variant=1233242016

https://ccafs.cgiar.org/blog/grand-greenhouse-plans-get-youths-farming-better-future#.Xg7rf0eQFnI

https://www.heritagelandbank.com/announcements/news-events/using-drip-irrigation-conserve-water-spring

Gardener Education

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Thank You to the Issaquah Grange for donating classroom space!

http://www.mgfkc.org/resources/growinggroceries